[Feature] Print Statements

[d0cd]

This PR adds support for print statements in Leo via core function calls, e.g Leo::print.
This is done by implementing a print instruction in an experimental branch of snarkVM.
While the opcode works, the output can be hard to parse when used in the Leo CLI.

For example, for this program:

program printer.aleo {
    transition main(a: u32, b: u32) -> u32 {
        let result: u32 = a + b;
        Leo::print(result);
        return result;
    }
}

the output of leo execute main 1u32 2u32 looks like

> leo execute main 1u32 2u32
       Leo ✅ Compiled 'printer.aleo' into Aleo instructions
2550859538u32
3u32
3u32
3u32
.
.
.

This is because the program is executed and evaluated multiple times in a single call to leo execute.
UX improvements are needed.